The present invention relates to position testing devices for a patient's body.
During certain medical procedures, such as an epidural anesthesia procedure, it is necessary to position the tip of a needle at a relatively precise position inside the patient's body. During this particular procedure, the needle tip should be located in the potential epidural space where the body pressure is normally slightly negative, and never positive. If the needle tip has been advanced too far into the body, it projects through the dura mater into the subarachnoid space where the body pressure is positive.
Epidural anesthesia has become popular among anesthesiologists and surgeons since it does not entail the risks associated with general anesthesia, and does not require that the dura mater be punctured. However, locating the epidural space can be relatively difficult since it is a potential space, i.e., an interface between two tissues which are normally held together by a slight negative pressure. Prior testing methods for the epidural space involve the use of tactile sense with syringes or a drop of liquid placed in the needle hub. The syringe tests have not been satisfactory since they rely on subjective judgment of the user under his control. The hub or Guiteras test also has not been suitable since the liquid drop frequently falls out of the hub, and thus may result in a false indication of the needle location.